1. Field of the Invention
The present invention relates to a cellular communication and, in particular, to a feedback system and method which is capable of efficiently collecting channel information from mobile stations (MSs) for cellular communication.
2. Description of the Related Art
Cellular wireless communication networks support the transmission of data between a base station and multiple user terminals. In such systems that support high-speed data transmission, the link from the base station to the mobile system requires high capacity. One mechanism to improve throughput is to schedule transmissions to user terminals based in part on their channel state information. This method, known as multi-user diversity, sends data to user terminals when their channel conditions are good. Unfortunately, acquiring feedback from multiple user terminals takes system resources away from the uplink channel, from the user terminals to the base station. Thus acquiring channel state information for many user terminals is difficult to perform in practice.
Opportunistic beamforming has been proposed as such a multi-user diversity method implemented with scheduling in cellular systems based on channel station information. The opportunistic beamforming method assumes that the channel information is received perfectly from each user terminal. The performance gain of multi-user diversity grows as the number of active users in the system becomes large. In the opportunistic beamforming method, however, the amount of channel information that needs to be fed back to the base station also increases with the number of users.
A threshold-based feedback mechanism has been proposed to exploit the multi-user diversity. The amount of feedback, however, still increases in proportion to the total number of user terminals in the threshold-based feedback mechanism.
An opportunistic splitting algorithm proposed for the uplink multiple access channel is algorithmically attractive, however, it does not solve the system level design issues of multi-user feedback, and it is not directly applicable to downlink multi-user scheduling. Further, it is may be limited to the algorithmic assumptions in real systems.